Methods: In a randomized, double-blind, placebo-controlled crossover trial, 50 adults (25 men, 25 women) with one or more cardiac risk factors were randomized to muscadine grape seed (MGS) supplement 1300mg daily vs.. placebo for 4 weeks each, with a 4-week washout between study periods. Resting diameter and endothelial function measured using brachial flow-mediated dilation (FMD) were determined at the beginning and end of each study period.